mailing-list issue

I could not register to xwiki-announce from http://forge.objectweb.org/mail/?group_id=170. ERROR MSG: <xwiki-announce-subscribe@objectweb.org>: host cvs.objectweb.org[194.199.16.17] said: 550 Unknown local part xwiki-announce-subscribe in <xwiki-announce-subscribe@objectweb.org> (in reply to RCPT TO command)